Dispensers of the aforementioned type are known for example from U.S. Pat. No. 6,695,246 and U.S. Pat. No. 6,069,354.
In for example the dispenser according to U.S. Pat. No. 6,695,246, the sensor control circuitry uses active IR (i.e. both IR emission and detection) to control sensing of the presence of a possible user. The IR is emitted in pulses. In the active IR mode, the presence of an object (i.e. a possible user) can be detected within a detection zone of about 12 to 24 cm from the dispenser and upon said detection operates a motor to dispense a hand towel to a user. One IR receiver and one IR emitter are located behind a front cover of the dispenser and each is mounted in a respective tube, the tubes being placed adjacent one another. By this arrangement the detection distance is kept short (between about 12 to 24 cm) so that objects which are outside the detection zone do not lead to undesired and unintentional dispensing. Likewise the object must be in the correct position and at a correct angle otherwise the tubes will prevent IR from being reflected back and collected by the receiver. Thus, while the possibility of undesirable reflections from other surfaces or the like is reduced, the sensor system requires fairly accurate positioning of the hand to effect operation. When an object is detected, the microprocessor activates the motor to dispense a towel if two scans with sufficient reflected IR are received by the IR sensing control system.
U.S. Pat. No. 6,069,354 discloses a dispenser using active IR which generates a square wave at about 1.2 kHz so as to emit a modulated IR signal, which is detected by reflection against a possible user to an IR detector (receiver). This document proposes using a sensor system set to sense a user between about 1.25 cm and about 30 cm distant from the dispenser. The IR emitter and the IR detector are both arranged very close together approximately midway up the front panel of the device while the discharge outlet is located at a lower part of the device. To operate the dispenser, the user thus raises a hand upwards above the discharge opening to where the IR sensor and emitter are placed.
In both of the above dispensers, a user's hand which is not correctly positioned with respect to the small area of detection of the sensors on the dispenser, i.e. in the small range of area detected and thus which does not immediately activate hand towel dispensing, will often be tempted to touch the dispenser to try and cause dispensing in the belief that touching of the casing close to the sensors is required, despite any written notices which the dispenser may contain in this regard. This is particularly the case because the user's hand is already at the height of the dispenser. This can result in lack of hygiene when several users consecutively touch the dispenser.
The present invention has as one of its objects, to provide an advantageous positioning of IR emitters and detectors (receivers) so as to provide good detection ability over a large area and to still avoid unintentional dispensing due to incorrect IR sensing.
A further object of the invention is to improve the positioning of the sensors in relation to the dispenser discharge outlet so that user detection occurs in an area of the dispenser where it is expected that a user's hands will normally be present for grasping a product issued by the dispenser, in particular by causing dispensing to occur without the user needing to raise his/her hands to the mounted height of the dispenser.
A further object is to improve the possibility of better hygiene.
Further objects of the invention will be apparent upon reading this specification.